Work machines such as track type tractors and a wide variety of other types of mining and earthmoving equipment often work in environments which give rise to speed control problems. For example, many different types of work machines are subject to potential engine and brake damage when operating on terrain which slopes, that is, when operating at various angles of inclination. Typically, any movement or pass on a slope where the work machine is not dozing, ripping, or performing other earthmoving type operations provides the opportunity for that particular work machine to be affected by gravity and to reach much faster speeds than it would normally reach under similar no load conditions on level terrain. In potential overspeed situations, the engine governor associated with some work machines may be controlled to respond to such a situation by shutting off fuel to the engine thereby retarding the ground speed of the machine. The engine is also capable of providing increased braking torque as the engine speed is driven higher due to the fact that the work machine is accelerating on the particular slope or inclination. Depending upon the particular work machine, there is some slope or inclination at which the weight of the work machine can drive the engine speed, or ground speed of the machine, beyond the speed capabilities of the particular work machine thereby resulting in damage or failure to the engine or power train system, typically, damage to the valve train. Also, as the terrain slope increases, the work machine achieves higher levels of kinetic energy which can be more difficult to dissipate depending upon the particular work and/or environmental conditions existing at the time.
Engine valve trains and brake systems can be developed to improve their overspeed and energy absorption capability. There are, however, economic and physical limitations to the amount of improvement which can be realistically achieved in these areas if a marketable product is to be produced.
It would therefore be desirable if there were provided a control system that would monitor the ground speed or engine speed of a particular work machine as it operates on an inclined surface and that would both manage and control the speed limit of the work machine based upon its operating slope or inclination. It would also be desirable if such a speed control system could also output appropriate signals to various speed retarding systems associated with a particular work machine to maintain the speed of the machine within proper operating speed limits while performing work on an inclined surface.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.